Added documentation on custom colors

docs/schema/theme.json

@@ -918,7 +918,8 @@
         "grey",
         "blue grey",
         "black",
-        "white"
+        "white",
+        "custom"
       ]
     },
     "accent": {
@@ -945,7 +946,8 @@
         "grey",
         "blue grey",
         "black",
-        "white"
+        "white",
+        "custom"
       ]
     },
     "icon": {

docs/setup/changing-the-colors.md

@@ -105,6 +105,8 @@ Click on a tile to change the primary color:
   })
 </script>
 
+See our guide below to learn how to set [custom colors].
+
   [Primary color support]: https://github.com/squidfunk/mkdocs-material/releases/tag/0.2.0
 
 #### Accent color
@@ -162,6 +164,8 @@ Click on a tile to change the accent color:
   })
 </script>
 
+See our guide below to learn how to set [custom colors].
+
   [Accent color support]: https://github.com/squidfunk/mkdocs-material/releases/tag/0.2.0
 
 ### Color palette toggle
@@ -323,6 +327,16 @@ properties). If you want to customize the colors beyond the palette (e.g. to
 use your brand-specific colors), you can add an [additional style sheet] and
 tweak the values of the CSS variables.
 
+First, set the [`primary`][palette.primary] or [`accent`][palette.accent] values
+in `mkdocs.yml` to `custom`, to signal to the theme that you want to define
+custom colors, e.g., when you want to override the `primary` color:
+
+``` yaml
+theme:
+  palette:
+    primary: custom
+```
+
 Let's say you're :fontawesome-brands-youtube:{ style="color: #EE0F0F" }
 __YouTube__, and want to set the primary color to your brand's palette. Just
 add: